1. FIELD OF THE INVENTION
This invention relates to a fan motor control and interlock circuit, primarily for use in conjunction with electric heaters including electric heat pumps.
2. BRIEF DESCRIPTION OF THE PRIOR ART
In accordance with the prior art, 24 volt AC coil relays were used to control the fan motors for electric furnaces including electric heat pumps. AC coil relays are more expensive than DC coiled relays and consume much less power than DC coil relays, therefore making it desirable to utilize less expensive circuitry. It is also desirable to utilize a printed circuit board to eliminate loose wires and the like which tend to cause problems. Furthermore, in the instance where many stages of electric heat would be employed, special care had to be given to the proper control wiring for each electric heat sequencer; or alternately, an "interlock" relay had to be used to insure that the first stage of electric heat was energized when the second or third stage was energized. If one of these two methods were not employed, an unsafe condition could occur in that an electric heater could be energized without the fan motor being powered.